If that mph is right the car has decent power. Big block A-body..........so what? 3000lbs. If that is accurate, for that mph, 700ish horsepower. HP based on the ET and weight would be 150 or so less. So the car is WAY down on power early. General consensus here is add gear and while that may help, the problem appears that the converter is way wrong or broken. 4.10 is enough gear. May not be optimal, but it's enough for this car to 60 way better than it does